Two new state-level data compilations should be bringing heartburn to Republicans and modest smiles to the lips of Democrats.

The first, released by Gallup, uses its 42,500 interviews conducted in 2005 to track party identification overall and by state.

Party identification is, of course different from party registration, with which it is sometimes confused. Party registration is a legal concept that measures how voters are signed up at the Board of Elections. By contrast, party identification is a psychological concept that measures individuals’ sense of association with one party or the other.

Despite all the commentary about the decline of parties and the rise of political independence, party identification is still far and away the best predictor of vote. According to the University of Michigan’s National Election Study, 91 percent of Democrats voted for Kerry, while 92 percent of Republicans cast their ballots for President Bush.

Gallup reports that in 2005 Democrats held a 4.5-point advantage over Republicans. That represents an increase of nearly two points compared to 2004 and even bigger gains over ’02 and ’03, when Democrats actually suffered small deficits.

At the state level, the news is even more encouraging. In 2005, 28 states and the District of Columbia had Democratic identification advantages of more than three points. Only 22 states fell into that category in 2004.

There are of course 56 Senate seats in these states, but also 333 electoral votes. Even if one removes all of the Southern and border states from the list, there are 24 states with 294 electoral votes where Democrats outnumber Republicans by at least three points. It takes 270 electoral votes to elect a president.

These party-identification results are reinforced by SurveyUSA’s latest 50-state roundup of presidential approval ratings. Just 45 percent or less approve of Bush’s performance in 33 states (plus D.C.), worth 403 electoral votes to Democrats. Keep in mind that in 2004 Bush did not win a single state where his approval rating dipped below 50 percent.

Of course neither party ID nor Bush approval provides a perfect forecast of things to come, but taken together they are powerful indicators. Twenty-seven states, worth 319 electoral votes, have Democratic margins of three points or more and have voters disapproving of Bush’s performance by a margin of 10 points or more.

But even before those electoral votes become relevant there are some hotly contested Senate races in what are now some of the most Democratic and Bush-hating states in the country.

Rhode Island, where Republican Sen. Lincoln Chafee is facing stiff competition, is the most Democratic state in the country (next to D.C.). Our party has a 34-point margin there, while voters disapprove of Bush by a vast 40-point margin.

In Missouri, Republican Sen. Jim Talent is running behind Democrat Claire McCaskill. During 2005, that state developed an eight-point Democratic advantage in party ID and Bush approval stands at just 41 percent.

Ohio, the scene of another hotly contested Senate race, now sports a seven-point Democratic edge in party identification, while Bush opponents outnumber supporters by 22 points. Republican Sen. Rick Santorum faces a double-digit deficit in Pennsylvania, a state with a 3.5-point Democratic edge where just 39 percent approve of the president’s performance.

Gallup has an admittedly small sample in Montana, where Republican Sen. Conrad Burns faces serious Abramoff problems. But it appears Republicans no longer have a cushion there, with party ID about even and voters evenly divided on Bush. Nevada has gone from a Republican plurality to a 12-point Democratic advantage, and Nevadans disapprove of Bush by a 20-point margin.

Of course things can change, but now is a difficult time to be a Republican.

Mellman is president of The Mellman Group and has worked for Democratic candidates and causes since 1982, including Sen. John Kerry (D-Mass.) in 2004.